An X-ray lens arrangement for forming a radiation pattern as a focal track is disclosed. The pattern comprises at least one 3-dimensional focal track of radiation. The aforesaid lens arrangement has a main axis passing through intensity weighted centroids of the X-ray source and the pattern. The lens arrangement includes at least one reflecting surface of continuously varying Rowland arcs. Each point belonging to the focal track is linked to each elemental point composing an emitting surface of said source by a corresponding Rowland arc.
